Commit 38a1f50a authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

phonet: do not call synchronize_rcu() from phonet_route_del() 



Calling synchronize_rcu() while holding rcu_read_lock() is not
permitted [1]

Move the synchronize_rcu() + dev_put() to route_doit().

Alternative would be to not use rcu_read_lock() in route_doit().

[1]
WARNING: suspicious RCU usage
6.12.0-rc5-syzkaller-01056-gf07a6e6ceb05 #0 Not tainted
-----------------------------
kernel/rcu/tree.c:4092 Illegal synchronize_rcu() in RCU read-side critical section!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor427/5840:
  #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
  #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
  #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: route_doit+0x3d6/0x640 net/phonet/pn_netlink.c:264

stack backtrace:
CPU: 1 UID: 0 PID: 5840 Comm: syz-executor427 Not tainted 6.12.0-rc5-syzkaller-01056-gf07a6e6ceb05 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:94 [inline]
  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
  lockdep_rcu_suspicious+0x226/0x340 kernel/locking/lockdep.c:6821
  synchronize_rcu+0xea/0x360 kernel/rcu/tree.c:4089
  phonet_route_del+0xc6/0x140 net/phonet/pn_dev.c:409
  route_doit+0x514/0x640 net/phonet/pn_netlink.c:275
  rtnetlink_rcv_msg+0x791/0xcf0 net/core/rtnetlink.c:6790
  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2551
  netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
  netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
  netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
  sock_sendmsg_nosec net/socket.c:729 [inline]
  __sock_sendmsg+0x221/0x270 net/socket.c:744
  sock_write_iter+0x2d7/0x3f0 net/socket.c:1165
  new_sync_write fs/read_write.c:590 [inline]
  vfs_write+0xaeb/0xd30 fs/read_write.c:683
  ksys_write+0x183/0x2b0 fs/read_write.c:736
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: 17a1ac00 ("phonet: Don't hold RTNL for route_doit().")
Reported-by: default avatarsyzbot <syzkaller@googlegroups.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Cc: Remi Denis-Courmont <courmisch@gmail.com>
Reviewed-by: default avatarJiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20241106131818.1240710-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 48171c65

net/phonet/pn_dev.c

+3 −2
Original line number Diff line number Diff line
@@ -406,8 +406,9 @@ int phonet_route_del(struct net_device *dev, u8 daddr) 


	if (!dev)

		return -ENOENT;

	synchronize_rcu();

	dev_put(dev);



	/* Note : our caller must call synchronize_rcu() and dev_put(dev) */



	return 0;

}

net/phonet/pn_netlink.c

+10 −2
Original line number Diff line number Diff line
@@ -233,6 +233,7 @@ static int route_doit(struct sk_buff *skb, struct nlmsghdr *nlh, 
{

	struct net *net = sock_net(skb->sk);

	struct nlattr *tb[RTA_MAX+1];

	bool sync_needed = false;

	struct net_device *dev;

	struct rtmsg *rtm;

	u32 ifindex;
@@ -269,13 +270,20 @@ static int route_doit(struct sk_buff *skb, struct nlmsghdr *nlh, 
		return -ENODEV;

	}



	if (nlh->nlmsg_type == RTM_NEWROUTE)

	if (nlh->nlmsg_type == RTM_NEWROUTE) {

		err = phonet_route_add(dev, dst);

	else

	} else {

		err = phonet_route_del(dev, dst);

		if (!err)

			sync_needed = true;

	}



	rcu_read_unlock();



	if (sync_needed) {

		synchronize_rcu();

		dev_put(dev);

	}

	if (!err)

		rtm_phonet_notify(net, nlh->nlmsg_type, ifindex, dst);